Is ONE PIECE episode 667 filler?
Canon No, episode 667 of ONE PIECE is canon.
#667
The Admiral's Decision! Fujitora vs. Doflamingo!
大将の決断 藤虎VSドフラミンゴ
Aired 26 Oct 2014
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.